Molecular Analysis Inc. (MAI) has developed an in situ hybridization procedure which is rapid (less than two hours), sensitive (can detect one molecule), inexpensive cost less than $1.00), and is non-isotopic. This procedure is ready for testing the feasibility of using it to detect the human immunodeficiency virus type 1 (HIV-1) in the peripheral blood of individuals with evidence of infection by HIV-1 or with no evidence of infection but at high risk for infection by HIV-1. We will obtain peripheral blood from 25 individuals in each of the four following categories: (1) with disease: acquired immunodeficiency syndrome (AIDS), AIDS-related complex, or Kaposi's sarcoma; (2) with no evidence of disease but seropositive for HIV-1; (3) with no evidence of disease but at high risk for HIV-1 infection and seronegative; (4) with no evidence of disease, at no risk for HIV-1 infection, and seronegative. On these 100 blood samples we will analyze all sera by ELISA and western blot for HIV-1 antibodies, all DNA by PCR and all peripheral blood cells by our proprietary in situ hybridization procedure. These data will allow us to compare our in situ results wi h@both serological testing and with a second DNA probe based test. If the rapid, inexpensive, non-isotopic detection of extremely small quantities of HIV-1 nucleic acid in peripheral blood is feasible, then MAI may have developed an extremely useful method to screen for or confirm the presence of active or latent AIDS virus in blood cells.